Mayor Thomas M. Menino said yesterday he will not attend Mayor-elect Martin J. Walsh’s Jan. 6 swearing-in ceremony — a perceived snub some political observers say signifies a deepening rift between the two pols.

“It’s usually considered a sign of good faith that you are having a proper transition of power from one administration to another. It’s a common courtesy. The fact that Menino is not going to be there suggests there is some sort of hostility there with his successor,” said Thomas J. Whalen, a Boston University social science professor.

“It’s kind of mean and small-minded. The idea of a democracy such as ours … we put aside our political differences and at least put forth the front that we are one and we are united,” Whalen added.

“Transparency was a centerpiece of the campaign, and Mayor-elect Walsh was very clear in public from the beginning that all independent expenditures should voluntarily disclose their donors,” Kate Norton, Walsh’s spokeswoman, said in a statement provided to the Globe Friday evening.

“The law prohibits any coordination between the campaign and any independent expenditure,” she said in the statement. “We don’t have any control over or awareness of their plans. Mayor-elect Walsh urged disclosure through statements to the press and sought to lead by example in providing complete transparency of his record, background, and contributions.”

Marty Walsh denies knowing AFT funded PAC ads

Mayor-elect Martin J. Walsh is claiming he had no idea the Boston teachers’ powerful national union was behind the last-minute, half-million-dollar ad drop by a mysterious PAC dubbed One Boston, whose pro-Walsh TV spot helped sweep him to victory in the campaign’s final weeks . . .

Walsh spokeswoman Kate Norton restated what the campaign said during the race, that they were prohibited by law from coordinating with outside groups, let alone knowing who was behind them.

Mayor Thomas M. Menino will not attend the inauguration of his successor, Martin J. Walsh, on Jan. 6. Dot Joyce, Menino’s spokeswoman, said he had already made plans to go on vacation by the time inaugural details were finalized. She said Menino believes the inauguration is “Marty Walsh’s day,” and the mayor will meet with him that morning to hand over the reins. Joyce said Menino does not wish to slight Walsh, but rather wants to honor the fact that he will be the new mayor. Menino’s decision was first reported by the Boston Herald.